One federal appeals court said Tuesday that tax subsidies in the Affordable Care Act could not be applied in 34 states while a second court upheld the law everywhere.

The 2-1 ruling by a three-judge panel of the U.S. Court of Appeals for the D.C. Circuit, which will be appealed by the government, threatens the framework of the Obamacare health care system for about 5 million Americans without employer-provided health plans and who are eligible for billions of dollars in tax subsidies.

Just two hours after that ruling, a separate federal appeals court panel in Richmond, Va., unanimously upheld the law and its system of subsidies and tax credits, putting it in opposition to the D.C. appeals court. That could raise the potential of a Supreme Court showdown.

The D.C. appeals panel ruled that as written, the health care law allows tax credits to be offered to qualified participants only in state-run exchanges. The administration had expected most if not all states to create their own, but only 16 states did so.

The court said the Internal Revenue Service went too far in allowing participants in other states served by the federal exchange to qualify for billions of dollars in government assistance. The aid has helped boost enrollment figures to more than 8 million.

Wisconsin did not establish an exchange and is one of the 34 relying on the federally run exchange.

Robert Kraig, executive director of Citizen Action of Wisconsin, a Milwaukee-based proponent of the Affordable Care Act, said people who have insurance through the exchanges should sit tight.

"Stay in the exchanges. If they leave, they can't come back until the next open-enrollment period. We will know a lot more by the time we get to open enrollment in November," he said. "Nobody is going to take away subsidies right now."

If the D.C. ruling were to stand, Kraig said it might put pressure on states such as Wisconsin to start its own exchange. Many of the states that did not establish exchanges are controlled by Republicans who opposed the Affordable Care Act. Such was the case in Wisconsin.

Kraig said the language of the law was poorly drafted, being clear about state exchanges and ambiguous about the federal exchanges, but the intent of Congress was clear.

"Congress could simply fix it, but, of course, that's a gridlock issue," he said. "States could be under tremendous pressure to create their own exchanges. It would make sense for Wisconsin to start planning in case this is upheld."

If allowed to stand, the ruling would blow a major hole in the law, since tax credits or subsidies are what make the private health insurance policies offered on the exchanges affordable to most Americans without employer-sponsored insurance plans.

"This is not theoretical. There are a lot of families that get their health care this way," Kraig said.